I think I know the answer to the speeding up thing on passing lanes - it is a spatial thing. Some people relate their speed to the width of the road based on a lifetime of driving around suburbs where narrow streets are slow streets and wide roads are fast roads. Their brain is programmed that way and out on the highway they drive slower on narrow highways and faster when the highway widens out - usually without knowing what they are doing. Having said that, some drivers just don't want to allow other vehicles to be in front of themselves. Also, there are the self appointed "truck police" who think truck drivers shouldn't travel faster than themselves. Added to that is the fact that many speedometers (BMW and VS especially) that can be 6 to 9 kph over their true speed and the owner doesn't know it.
As for truck drivers always wanting to travel at the speed limit, it must be understood that there are two good reasons for that. Truck drivers are paid by the kilometer, so at 44 cents per kilometer (B-Double casual driver rate a couple of years ago) = $44.00 per hour (hypothetical given that the eventual average speed for a B-Double between cities in Australia is 84 kph and 87 kph for a semi trailer). Now two things can happen; 1. If you slow the driver down by traveling at 80 kph, you reduce his hourly rate by 20%, remembering that a standard truck licence only allows 12 hours driving per day and, therefore, he/she cannot make up the lost income by driving extra hours. Imaging if a public servant or a member of the prima donna unions was made to work more slowly and told that their income would be reduced accordingly. 2. If he/she can only drive at 80% of the permissible speed he/she may not be able to reach a destination within the 12 hours or may not be able to meet a deadline that is otherwise a reasonable deadline.
Not wishing to create an argument here, but pointing out why truck drivers express their feelings the way they sometimes do. The road is their workplace and it is unreasonable for grey nomads to expect truck drivers to drive below the speed limit because said grey nomad prefers to reduce fuel consumption, or is not competent to drive at the speed limit when it is prudent and safe to do so, or is driving a rig that is not set up safely enough to travel at the speed limit when it is prudent to do so. In my opinion it is wise and reasonable to expect grey nomads, and others, to drive at the speed limit for that period of time necessary to get to a point in the road where it is safe for the truck to overtake.
Where is that "duck" smiley.
I have been in a truck on a few occasions and have seen the penile cranium car drivers but there is one big difference and that is size and some of those truck drivers are just down right A holes. I do the same thing with penile cranium car drivers ie take #'s and report them as well so I am not picking on the sweet dear old truckies. 
